Hepatocellular carcinoma (HCC) is a rapidly increasing form of cancer in the United States, with ~ 14,000 deaths annually, ranking it as the 8th cause of cancer mortality. HCC is a highly malignant tumor type with the overall 1-year survival rate below 50% and the 5-year survival below 10%. Although progress has been made in interventional procedures for treating HCC in situ, the most successful recent chemotherapeutic developed, soranfenib only increased the median survival rate of patients from 7.9 to 10.7 months. Thus, alternate strategies are needed for HCC not amenable to surgery. The long-range goal of this project is to develop an effective RNA inhibition (RNAi) strategy targeting only the cancer cells for treatment of HCC. To accomplish this objective, this R21 is a proof-of-concept that will determine the utility of this approach using tumor-targeted delivery of a sub 50 nanometer (s50) encapsulated nucleic acid RNAi therapeutic targeting the key regulatory protein, casein kinase II (CK2) in treating HCC. The two Specific Aims proposed are designed to test the hypothesis that coupling the novel nonviral s50 nanocapsule that provides cell-type specific delivery to the liver in vivo, by use of an alternate ligand, tenfibgen (TBG), can effectively direct RNAi targeting CK2 specifically to the HCC tumors; and disabling CK2 activity via RNAi will effectively reduce or potentially clear the HCC in the animals as observed in mouse xenograft models of head neck and prostate cancer. Specific Aim 1, is designed to characterize and compare in vitro the uptake and specificity of TBG s50 nanocapsules containing RNAi targeting CK2? and ?' catalytic subunits to effectively silence CK2 activity in human and rat HCC cell lines and WB-F344 a normal rat hepatocyte cell line. The rationale for disabling CK2 activity is it has been identified as a key target involved in cancer signaling pathways, promoting tumorigenesis, is implicated directly in HCC proliferation and resistance to cell death. In contrast, inhibition of CK2 activity promotes HCC cell death as well as restoring their sensitivity to currently employed small molecule chemotherapeutic drugs making it an attractive target for treatment of HCC. Specific Aim 2 will examine the specificity of the delivery system in vivo via neutron activation analysis for the biodistribution of the TBG nanocapsules and the effectiveness of the anti-CK2 RNAi therapeutic strategy in treating HCC in a syngeneic heterotopic rat model. If successful, this will represent a major advance of this therapeutic strategy towards our ultimate goal, human clinical use having successfully transitioned from mouse xenograft models to an immunocompetent heterotopic rat model, a failure point enroute to the clinic for many promising therapies. Moreover, many potential anticancer agents too toxic to administer systemically may be possible to use with the TBG s50 tumor-cell specific delivery in vivo, reviving effective but systemically toxic anti-HCC therapeutics for clinical use.